Relief valve for gas

ABSTRACT

A relief valve for gas includes: a housing having a valve port connecting with an inflow passage and an outflow passage, and a tapered valve seat formed in the inflow passage to surround the valve port; a valve body having a tapered valve head part and movable between a closed position where the valve head part is seated and fits in the valve seat to close the valve port, and a full stroke position farthest from the valve seat; and a biasing member that biases the valve body to the closed position. The valve body has a seal member that is provided to externally fit on a seal groove formed on an outer circumferential face of the valve head part over an entire circumferential periphery, and to be seated on the valve seat in the closed position to seal between the valve seat and the valve head part.

TECHNICAL FIELD

The present invention relates to a relief valve for gas for keeping thepressure of the gas flowing in a flow channel at a predeterminedpressure or less.

BACKGROUND ART

A flow channel is provided with a relief valve for gas so as to preventthe pressure of the gas flowing in the flow channel from exceeding apredetermined value, and one example of such a relief valve isdisclosed, for example, in PTL 1. The relief valve of PTL 1 has aseating member in a tip end part, namely, in a valve head of the valvebody, and by seating the seating member on the protruding valve seat insuch a manner that the seating member is pushed against the valve seat,the valve port is closed.

CITATION LIST Patent Literature

-   PTL 1: Japanese Laid-Open Patent Application Publication No.    2014-135219

SUMMARY OF INVENTION Technical Problem

In the relief valve of PTL 1, a sheet member made of synthetic rubber isvulcanization-bonded to the valve body made of metal. The shape of thevalve seat is complicated to keep the valve opening pressure constant,so that the valve seat is difficult to process. Therefore, reduction inthe manufacturing cost of relief valves is limited.

In light of the above, it is an object of the present invention toprovide a relief valve for gas capable of reducing the manufacturingcost.

Solution to Problem

A relief valve for gas of the present invention includes: a housinghaving a valve port connecting with an inflow passage and an outflowpassage, and a valve seat with a tapered shape formed in the inflowpassage to connect with the valve port; a valve body having a valve headpart with a tapered shape and movable between a closed position wherethe valve head part is seated such that the valve head part is fit inthe valve seat to close the valve port, and a full stroke positionfarthest from the valve seat; and a biasing member that biases the valvebody to locate the valve body in the closed position, and the valve bodyhas a seal groove provided on an outer circumferential face of the valvehead part over an entire circumferential periphery, and a seal memberprovided to externally fit on the seal groove and to be seated on thevalve seat in the closed position to seal between the valve seat and thevalve head part.

According to the present invention, since the valve port is closed byseating the seal member on the tapered valve seat, the valve seat can beformed into a tapered shape. Accordingly, there is no need to make acomplicated processing on the valve seat, and the manufacturing cost ofrelief valves for gas can be reduced. In addition, since the seal memberis externally fit on the seal groove, the seal member is easy to attach.Accordingly, the manufacturing cost of relief valves for gas can bereduced.

In the above invention, the valve seat may have a tapered shape, andhave a proximal part and a distal part having different taper angles,the distal part may be located farther from the valve port than theproximal part so as to seat the valve head part when the valve body islocated in the closed position, and the proximal part may have a moreobtuse taper angle than the distal part.

According to the above configuration, it is possible to further reducethe switchover lift amount. This makes it possible to reduce the timeduring which the seal member is exposed to large differential pressureat the time of opening the valve, and further prevent the seal memberfrom deforming and being damaged, and coming off from the seal groove.

In the above invention, the taper angle of the proximal part maycontinuously change such that the taper angle increases toward the valveport.

According to the above configuration, it is possible to further reducethe switchover lift amount. This makes it possible to reduce the timeduring which the seal member is exposed to large differential pressureat the time of opening the valve, and further prevent the seal memberfrom deforming and being damaged, and coming off from the seal groove.

In the above invention, the inflow passage may be provided with arestrictor. According to the above configuration, it is possible toreduce the pressure of the gas flowing downstream the restrictordirectly after opening the valve. This makes it possible to reduce thedifferential pressure acting on the seal member directly after openingthe valve, and prevent the seal member from deforming and being damaged,and coming off from the seal groove.

In the above invention, the seal member may be arranged to fit in theseal groove, and the seal groove may have a curved surface shape inwhich a section of a lateral face of a secondary side is concave.

According to the above configuration, since the seal member can bepushed into the part of the curved surface shape when the seal member ispushed toward the secondary side, it is possible to prevent the sealmember from falling off. Also, by designing the seal groove to have sucha shape, it is possible to reduce the variation in the pressurenecessary for moving the valve body to open the valve port, namely, thevalve opening pressure.

Advantageous Effects of Invention

According to the present invention, it is possible to reduce themanufacturing cost.

The above objects, other objects, features, and merits of the presentinvention will be apparent from the following detailed description ofpreferred embodiments with reference to attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a relief valve for gas according toEmbodiment 1 of the present invention.

FIG. 2 is a sectional view showing the state after the relief valve forgas of FIG. 1 is open.

FIG. 3 is a sectional view showing a full stroke state of the reliefvalve for gas of FIG. 1.

FIG. 4 is an enlarged sectional view of region X1 shown in FIG. 1.

FIG. 5 is an enlarged sectional view of region X2 shown in FIG. 2.

FIG. 6 is an enlarged sectional view of region X3 shown in FIG. 3.

FIGS. 7(a) and (b) are sectional views showing, in an enlarged scale,part of a relief valve for gas according to Embodiment 2, wherein FIG.7(a) is an sectional view of the relief valve for gas in a valve closedstate, and FIG. 7(b) is a sectional view of the relief valve for gas ina valve open state.

FIGS. 8(a) and (b) are sectional views showing, in an enlarged scale,part of relief valves for gas according to Embodiment 3 and Embodiment4, wherein FIG. 8(a) is a sectional view of the relief valve for gasaccording to Embodiment 3, and FIG. 8(b) is a sectional view of therelief valve for gas according to Embodiment 4.

FIG. 9 is a sectional view of a relief valve for gas according toEmbodiment 5.

DESCRIPTION OF EMBODIMENTS

Hereinafter, relief valves for gas 1, 1A to 1D according to Embodiments1 to 5 of the present invention are described by referring to drawings.The concept of direction used in the following description is merelyused for convenience in description, and should not be understood tolimit the orientation or the like of the configuration of the inventionto the described direction. The relief valves for gas 1, 1A to 1Ddescribed below each are merely one embodiment of the present invention.Therefore, the present invention is not limited to the embodiments, andaddition, deletion, and modification can be made without departing fromthe scope of the invention.

Embodiment 1

A high pressure gas tank stores high pressure gas, for instance, gas at30 to 100 MPa, and is provided with valves having various functions soas to charge or discharge the high pressure gas to/from the highpressure gas tank. One example of such valves is a pressure reducingvalve that reduces the pressure of the high pressure gas to bedischarged from the tank to about 1 MPa, and as a safety device thereof,a relief valve for gas 1 shown in FIG. 1 is provided. The relief valvefor gas 1 is provided, for example, in a valve block attached to thehigh pressure gas tank (not shown) or provided independently of thevalve block, and when the pressure of the working gas flowing in theflow channel (not shown) exceeds a predetermined pressure, the reliefvalve is open to release the working gas outside. The relief valve forgas 1 having such function is configured as follows.

That is, the relief valve for gas 1 includes a housing 2, a valve body3, and a coil spring 4, and the housing 2 principally has a housing body11 and a lid body 12. The housing body 11 has a valve chamber 21 with asubstantially bottomed cylindrical shape, and an opening part thereof isclosed by the lid body 12 inserted therein. Further, the housing body 11has an inflow passage 23 and an outflow passage 24. The inflow passage23 extends along axial line L1 of the valve chamber 21, and connects atone end with the aforementioned flow channel, and opens at the other endto the valve chamber 21 via a valve port 22 on a bottom face 21 a of thevalve chamber 21. The outflow passage 24 opens at one end on thecircumferential face of the valve chamber 21, and connects at the otherend with the outside. The outflow passage 24 is not necessarily open onthe circumferential face of the valve chamber 21, but may be formed inthe lid body 12. In this manner, the two passages 23, 24 are connectedwith each other via the valve port 22, so that the working gas flowingin the flow channel can be discharged outside. On the other hand, thevalve chamber 21 accommodates the valve body 3 and the coil spring 4 soas to stop discharge of the working gas by closing the valve port 22.

The valve body 3 is a substantially bottomed cylindrical member, and isaccommodated in the valve chamber 21 movably along axial line L1 andapart from the lid body 12. More specifically, the valve body 3 has aninner hole 3 a, and is accommodated in the valve chamber 21 in such amanner that the open end of the inner hole 3 a is opposed to the lidbody 12. The lid body 12 has a recess part 12 a in a part opposed to thevalve body 3. The inner hole 3 a, together with the recess part 12 a,forms a spring accommodation chamber 13, and the spring accommodationchamber 13 accommodates the coil spring 4.

The coil spring 4 which is one example of a biasing member is aso-called helical compression spring, and the coil spring 4 is receivedat one end by the lid body 12, and at the other end by a bottom face 3 bof the valve body 3. Therefore, the valve body 3 is biased by the coilspring 4 to leave the lid body 12 in the direction toward the valve port22, that is, toward the closed position as shown in FIG. 1. The coilspring 4 may be substituted by a flat spring, an elastic body, amagnetic spring, an air spring, a pushing mechanism by electrostaticforce and the like. The valve body 3 biased by the coil spring 4 in thismanner has a valve head part 3 c on the side opposite to the open end,namely, in a tip end side part. The valve head part 3 c has a taperedshape, more specifically a substantially truncated conical shape, and isformed such that the outer diameter of the tip end is smaller than theaperture of the valve port 22, and the outer diameter of the base endside is larger than the aperture of the valve port 22. Therefore, thevalve head part 3 c can be inserted into the inflow passage 23 via thevalve port 22 over the range from the tip end to a middle part of thevalve head part 3 c. Also, a valve seat 25 is formed in the inflowpassage 23 so as to seat a seat part 3 d which is an insertable part ofthe valve head part 3 c.

The valve seat 25 is formed in a part near the valve port 22 of theinflow passage 23 in the housing body 11, namely, in a part connectingwith the valve port 22 of the inflow passage 23 in the presentembodiment. Still more specifically, the valve seat 25 is formed in theinflow passage 23 to surround the valve port 22, and has substantiallythe same shape as the seat part 3 d. In other words, the valve seat 25forms a tapered shape, and a taper angle θ of the valve seat 25 issubstantially the same as a half vertical angle α (=θ) of the valve headpart 3 c. Therefore, the seat part 3 d can be seated on the valve seat25 such that the seat part 3 d is fit in the valve seat 25 to close thevalve port 22. The half vertical angle α of the valve head part 3 csatisfies, for example, 10°≤α≤45°, and in the present embodiment, thehalf vertical angle α is 30°. On the outer circumferential face of theseat part 3 d, a seal groove 3 e is formed. The seal groove 3 e isformed at distance s from the tip end of the valve head part 3 c, and isformed on the outer circumferential face of the seat part 3 d over theentire periphery. The section of the seal groove 3 e has a substantiallyflat oval shape, and to the seal groove 3 e a seal member 5 is attachedso as to seal between the valve seat 25 and the seat part 3 d in aseated position.

The seal member 5 is a synthetic rubber member having a substantiallyannular shape, and is, for example, an O ring in the present embodiment.The seal member 5 may be any annular seal without limited to an O ring.The section of the seal member 5 may be, for example, a trapezoidalsection and a D-shaped section other than a circular section, and thesection shape does not matter. The seal member 5 is attached to theouter circumferential face of the seat part 3 d, namely, the outercircumferential face of the valve head part 3 c such that the sealmember is fit in the seal groove 3 e. The section (more specifically,the section perpendicular to the circumferential direction) of the sealgroove 3 e has a substantially flat oval shape as described above, andlateral faces (that is, lateral faces on both sides in the longitudinaldirection of the seal groove 3 e) of a primary side (that is, theupstream side, and the tip end side of the valve head part 3 c) and asecondary side (that is, the downstream side, and the base end side ofthe valve head part 3 c) have substantially semicircular shapes. Thatis, the seal groove 3 e has such a curved surface shape that the sectionof the lateral face of the primary side is concave, and the section ofthe lateral face of the secondary side is concave. The seal groove 3 ehaving such a shape has a return in the downstream side part, andachieves the following effects. That is, when the seal member 5 ispushed by the gas at the time of opening the valve, the seal member 5can be pushed into the downstream side part, so that the seal member 5is hard to fall off. In addition, by employing such a shape, it ispossible to reduce the variation in the pressure necessary for movingthe valve body 3 to open the valve port 22, namely, the variation in thevalve opening pressure. While only the seal member 5 is disposed in theseal groove 3 e in the present embodiment, a backup ring in addition tothe seal member 5 may be fit in to prevent the seal member 5 fromfalling out of the seal groove 3 e.

Inside diameter D2 of the seal member 5 arranged in this mannersatisfies the relation of D2≥D1×1.14 with pore diameter D1 of the inflowpassage 23, and also the seal groove 3 e is formed to allow the sealmember 5 to fit therein. Further, wire diameter w of the seal member 5is larger than depth d of the seal groove 3 e, and the seal member 5 isso designed that part of the seal member 5 protrudes from the sealgroove 3 e in the attached state (see, for example, FIG. 2 and FIG. 3).Therefore, the seal member 5 can come into close contact with the valveseat 25 over an entire circumferential periphery when seated, andclosely seal between the seat part 3 d and the valve seat 25 (see FIG. 1and FIG. 4). The valve body 3 configured as described above is furtherconfigured as follows.

That is, the valve body 3 has a base end side part having substantiallythe same diameter as the circumferential face of the valve chamber 21,and is guided by the circumferential face of the valve chamber 21 in asliding manner. On the other hand, the remaining part including thevalve head part 3 c has a smaller diameter than the circumferential faceof the valve chamber 21, and is surrounded by a valve passage 26 havinga substantially annular shape. The valve passage 26 always connects withthe outflow passage 24, and comes into connection with the inflowpassage 23 when the valve port 22 is open. That is, when the valve body3 leaves the valve seat 25 to open the valve port 22, the two passages23, 24 connect with each other via the valve passage 26, and the workinggas in the flow channel is released outside. Specifically, the valvebody 3 has a communicating path 3 f for allowing expansion andcontraction of the spring accommodation chamber 13.

The relief valve for gas 1 configured as described above operates asfollows. In the relief valve for gas 1, the working gas flowing in anunillustrated flow channel is guided to the inflow passage 23, and thepressure of the guided working gas acts on the tip end of the valve body3, namely, the tip end of the valve head part 3 c. Then, as the pressureof the unillustrated flow channel increases to reach a predetermined setpressure, the valve body 3 is lifted against the biasing force of thecoil spring 4 (see FIG. 2). As a result, the valve body 3 leaves thevalve seat 25 (more specifically, the seal member 5 leaves the valveseat 25) to form an annular passage 30 between the valve body 3 and thevalve seat 25, and the valve port 22 is opened (see FIG. 5). The workinggas enters the valve passage 26 through the annular passage 30, and isreleased outside through the outflow passage 24 (see the arrow in FIG.5). By releasing part of the working gas flowing in the flow channeloutside in this manner, the pressure of the working gas flowing in theflow channel is prevented from increasing to a predetermined setpressure or more.

Even after leaving the valve seat 25, the valve body 3 is kept lifted tofurther extend the annular passage 30 to release the working gas outsideat a larger flow rate. The valve body 3 is further lifted and when thelift amount from the closed position reaches full lift amount LF, thevalve body 3 comes into abutment with the lid body 12 as shown in FIG.3, and the valve body 3 stops at that position, namely, a full strokeposition (see FIG. 3 and FIG. 6). In this manner, the valve body 3 canstroke from the closed position shown in FIG. 1 to the full strokeposition shown in FIG. 3. On the other hand, in the relief valve for gas1, when the working gas is released outside and the pressure of theworking gas in the inflow passage 23 decreases, the valve body 3 ismoved toward the closed position to reduce the releasing flow rate.Then, when the pressure of the working gas decreases to less than apredetermined set pressure, the valve body 3 is seated on the valve seat25 to close the valve port 22.

In the relief valve for gas 1 having such a function, the seal member 5seals between the valve head part 3 c and the valve seat 25 (see FIG.4), and in order to achieve this, the seal member 5 protrudes from thevalve head part 3 c as described above (see FIG. 5 and FIG. 6). Sincethe protruding seal member 5 is brought into abutment with the valveseat 25 to achieve the sealing, slight gap c is generated between thevalve head part 3 c and the valve seat 25 even when the valve is closed(see FIG. 4). Therefore, directly after opening the valve (that is,directly after the valve body 3 leaves the valve seat 25), the sealmember 5 forms a throat 31 with the valve seat 25, and largedifferential pressure is generated at the upstream side and thedownstream side of the seal member 5 by the throat 31. It is assumedthat the differential pressure continuously acts on the seal member 5 todeform the seal member 5, and the seal member 5 comes off from the sealgroove 3 e. To prevent occurrence of such a situation, the relief valvefor gas 1 is configured as follows.

That is, in the relief valve for gas 1, the annular passage 30 graduallyextends as the valve body 3 lifts (that is, strokes toward one end ofthe axial direction). Since the valve body 3 and the valve seat 25 havetapered shapes, the rate of change in flow channel area of the annularpassage 30 at the time of lifting differs depending on the position.More specifically, the rate of change in flow channel area in relationto the lift amount is larger on the base end side compared with the tipend side of the valve head part 3 c. The flow channel area between theseal member 5 and the valve seat 25 (hereinafter, the flow channel arearefers to an area of the section cut in the plane perpendicular to aseat face 25 a of the valve seat 25) shows a larger rate of changecompared with the flow channel area between the tip end of the valvebody 3 and the valve seat 25 because the sealing member 5 is disposedfar from the tip end. Therefore, as the valve body 3 strokes in theopening direction from the closed position, the two flow channel areasreverse at predetermined switchover lift amount LS in course of time. Inother words, as the valve body 3 strokes by switchover lift amount LS toreach a switchover position, the position where a throat is formed inthe annular passage 30, namely, a formation position is switched to athroat 32 from the throat 31.

The relief valve for gas 1 configured as described above exerts thefollowing operation and effect. That is, in the relief valve for gas 1,the seal member 5 can come off from the valve port 22 while the valvebody 3 strokes from the closed position to the full stroke position. Itis assumed that the pressure of the working gas discharged from theannular passage 30 is not sufficiently reduced, and high in the vicinityof the valve port 22. The seal member 5 comes off from the valve port 22and leaves there, and thus the seal member 5 can be prevented from beingexposed to the high pressure working gas. This makes it possible toprevent the seal member 5 from deforming and being damaged, and comingoff from the seal groove 3 e. On the other hand, since distance sbetween the tip end of the valve head part 3 c and the seal groove 3 e,namely, distance s between the tip end of the valve head part 3 c andthe seal member 5 is set to be smaller than full lift amount LF, it ispossible to guide the working gas to the valve chamber 21 while reducingthe pressure of the working gas in the annular passage 30. Therefore, itis possible to prevent the seal member 5 from being exposed to highpressure.

Furthermore, in the relief valve for gas 1, since the seal member 5 isprovided to externally fit on the seal groove 3 e, the seal member 5 iseasy to attach to the valve body 3. Therefore, the manufacturing cost ofthe relief valve for gas 1 can be reduced. Particularly in the reliefvalve for gas 1, by externally fitting the seal member 5 on the sealgroove 3 e, it is possible to eliminate the need of vulcanizationbonding as in conventional arts, and it is possible to further reducethe manufacturing cost of the relief valve for gas 1.

Also, in the relief valve for gas 1, since the seal member 5 is seatedon the valve seat 25 with a tapered shape to close the valve port 22,the valve seat 25 can be formed into a tapered shape. Accordingly, thereis no need to make a complicated processing on the valve seat 25, andthe manufacturing cost of the relief valve for gas 1 can be reduced.

Also, in the relief valve for gas 1, inside diameter D2 of the sealmember 5 and pore diameter D1 of the inflow passage 23 satisfy therelation of D2≥D1×1.14. Therefore, the seal member 5 can be disposedapart from the distal end of the valve seat 25 (namely, the open end ofthe inflow passage 23), so that the formation position of the throat canbe switched earlier from the seal member 5 to other position. Also, bydisposing the seal member 5 apart from the distal end of the valve seat25, the seal member 5 can be disposed apart from the tip end of thevalve body 3, so that it is possible to secure the space for forming theseal groove 3 e. Accordingly, it is possible to form the seal groove 3 ein an appropriate form, or in other words, it is possible to form thesection of the seal groove 3 e into a substantially flat oval shape asdescribed above. This makes it possible to fit the seal member 5 in theseal groove 3 e without damaging the seal member 5, and improve theassemblability of the seal member 5.

Embodiment 2

The relief valve for gas 1A of Embodiment 2 resembles the relief valvefor gas 1 of Embodiment 1 in configuration. Therefore, the configurationof the relief valve for gas 1A of the second embodiment is mainlydescribed about the point different from that of the relief valve forgas 1 of the first embodiment, and the same configuration is denoted bythe same reference numeral, and the description thereof is omitted. Thesame applies also to later-described relief valves for gas 1B to 1D ofEmbodiments 3 to 5.

The relief valve for gas 1A of Embodiment 2 includes the housing 2, avalve body 3A, and the coil spring 4 as shown in FIG. 7(a), and thevalve body 3A is configured as follows. That is, the valve head part 3 cof the valve body 3A has a substantially conical shape, and has a tipend part extending beyond the valve seat 25. Therefore, in the reliefvalve for gas 1A, the position where the flow channel area minimizes ateach position of the annular passage 30 other than positions between theseal member 5 and the valve seat 25 is as follows. That is, the flowchannel area of the annular passage 30 minimizes between the distal end(namely, the open end on the side far from the valve port 22 in thevalve seat 25) 25 b of the valve seat 25 and the valve head part 3 c(see FIG. 7(b)). The change in flow channel area between the distal end25 b and the valve head part 3 c is gentler than the change in flowchannel area between the tip end of the valve body 3 and the valve seat25 in Embodiment 1. Therefore, in the relief valve for gas 1A,switchover lift amount LS2 thereof can be made smaller than switchoverlift amount LS in Embodiment 1. This makes it possible to reduce thetime during which the seal member 5 is exposed to large differentialpressure at the time of opening the valve, and to further prevent theseal member 5 from deforming and being damaged, and coming off from theseal groove 3 e.

Besides the above, the relief valve for gas 1A of Embodiment 2 exertsthe same operation and effect as the relief valve for gas 1 ofEmbodiment 1.

The valve head part 3 c of the valve body 3A does not necessarily have asubstantially conical shape, but may have a substantially truncatedconical shape likewise the valve head part 3 c of Embodiment 1 as longas the valve head part 3 c extends beyond the valve seat 25, and the tipend of the valve head part 3 c is located on the distal end side thanthe valve seat 25 in the inflow passage 23.

Embodiment 3

The relief valve for gas 1B of Embodiment 3 includes a housing 2B, thevalve body 3, and the coil spring 4 as shown in FIG. 8(a), and a valveseat 25B of the housing 2B is configured as follows. That is, the valveseat 25B has a distal part 35 a located far from the valve port 22, anda proximal part 35 b located near the valve port 22. Both the distalpart 35 a and the proximal part 35 b are tapered, and respectively havetaper angles θ1, θ2 that are different from each other. Specifically,the taper angle θ2 of the proximal part 35 b is more obtuse than thetaper angle θ1 of the distal part 35 a. Accordingly, the valve seat 25extends outward in the radial direction toward the valve port 22. Theseal member 5 is arranged to be seated on the distal part 35 a.

In the relief valve for gas 1B configured as described above, bydesigning the taper angle θ2 of the proximal part 35 b of the valve seat25 to be larger than the taper angle θ1 of the distal part 35 a, it ispossible to switch the formation position with a smaller lift amountcompared with the relief valve for gas 1 of Embodiment 1. This makes itpossible to further prevent the seal member 5 from deforming and beingdamaged, and coming off from the seal groove 3 e.

Besides the above, the relief valve for gas 1B of Embodiment 3 exertsthe same operation and effect as the relief valve for gas 1 ofEmbodiment 1.

Embodiment 4

The relief valve for gas 1C of Embodiment 4 includes a housing 2C, thevalve body 3, and the coil spring 4 as shown in FIG. 8(b), and a valveseat 25C of the housing 2C is configured as follows. That is, the valveseat 25C has a distal part 36 a located far from the valve port 22, anda proximal part 36 b located near the valve port 22. Both the distalpart 36 a and the proximal part 36 b are tapered, and respectively havetaper angles θ1, θ3 that are different from each other. Specifically,the taper angle θ3 of the proximal part 36 b is larger than the taperangle θ1 of the distal part 36 a. The taper angle θ3 of the proximalpart 36 b continuously changes, and increases toward one end of theaxial direction, namely, the valve port 22. The proximal part 36 bhaving such a shape has a rounded shape in the present embodiment.

The relief valve for gas 1C of Embodiment 4 configured as describedabove exerts the same operation and effect as the relief valve for gas1B of Embodiment 3.

Embodiment 5

In the relief valve for gas 1D of Embodiment 5, an inflow passage 23Dhas a restrictor 37 as shown in FIG. 9. The restrictor 37 is capable ofreducing the pressure of the gas on the side downstream the restrictor37 at the time of opening the valve. That is, the pressure of theannular passage 30 can be controlled. This makes it possible to reducethe differential pressure acting on the seal member 5 directly afteropening the valve, and prevent the seal member 5 from deforming andbeing damaged, and coming off from the seal groove 3 e.

The relief valve for gas 1D of Embodiment 5 configured as describedabove exerts the same operation and effect as the relief valve for gas 1of Embodiment 1.

OTHER EMBODIMENTS

While the relief valves for gas 1, 1A to 1D of Embodiments 1 to 5 areprovided in the flow channel that discharges the working gas from thehigh pressure gas tank, they are not necessarily provided in such a flowchannel. In other words, the relief valves for gas 1, 1A to 1D ofEmbodiments 1 to 5 may be provided in a flow channel in which lowpressure gas flows, and the application thereof does not matter.

Various modifications and other embodiments of the present inventionwill be apparent to those skilled in the art from the above description.Therefore, the above description should be interpreted merely asillustration, and is provided for the purpose of indicating the bestmode for carrying out the present invention to those skilled in the art.The details of the structure and/or the function can be substantiallychanged without departing from the spirit of the present invention.

REFERENCE CHARACTERS LIST

-   -   1, 1A to 1C relief valve for gas    -   2, 2B, 2C housing    -   3, 3A valve body    -   4 coil spring    -   5 seal member    -   21 valve chamber    -   21 a bottom face    -   22 valve port    -   23 inflow passage    -   24 outflow passage    -   25, 25B, 25C valve seat    -   31 throat    -   32 throat    -   33 valve head part    -   33 b tip end part    -   34 annular narrow path (throat)    -   35 valve seat    -   35 a, 36 a distal part    -   35 b, 36 b proximal part

1. A relief valve for gas comprising: a housing having a valve portconnecting with an inflow passage and an outflow passage, and a valveseat with a tapered shape formed in the inflow passage to connect withthe valve port; a valve body having a valve head part with a taperedshape, the valve body being movable between a closed position where thevalve head part is seated such that the valve head part is fit in thevalve seat to close the valve port, and a full stroke position farthestfrom the valve seat; and a biasing member that biases the valve body tolocate the valve body in the closed position, the valve body having aseal groove provided on an outer circumferential face of the valve headpart over an entire circumferential periphery, and a seal memberprovided to externally fit on the seal groove and to be seated on thevalve seat in the closed position to seal between the valve seat and thevalve head part.
 2. The relief valve for gas according to claim 1,wherein the valve seat has a tapered shape, and has a proximal part anda distal part having different taper angles, the distal part is locatedfarther from the valve port than the proximal part so as to seat thevalve head part when the valve body is located in the closed position,and the proximal part has a taper angle that is more obtuse than a taperangle of the distal part.
 3. The relief valve for gas according to claim2, wherein the taper angle of the proximal part continuously changessuch that the taper angle increases toward the valve port.
 4. The reliefvalve for gas according to claim 1, wherein the inflow passage isprovided with a restrictor.
 5. The relief valve for gas according toclaim 1, wherein the seal member is arranged to fit in the seal groove,and the seal groove has a curved surface shape in which a section of alateral face of a secondary side is concave.